stdlib dirname does not understand Windows paths

dirname does not remove the last part of Windows paths:

In the example below dirname(C:\Windows\system32) is '.' . I think the output should be "C:\Windows"

notify

{ "\$::system32 $::system32" : }

$dirname32 = dirname($::system32)
notify

{ "\$dirname32 $dirname32" : }

Output.

Notice: $dirname32 .
Notice: /Stage[main]/Winnodes/Notify[$dirname32 .]/message: defined 'message' as
'$dirname32 .'
Notice: $::system32 C:\Windows\system32
Notice: /Stage[main]/Winnodes/Notify[$::system32 C:\Windows\system32]/message: d
efined 'message' as '$::system32 C:\Windows\system32'
Notice: Finished catalog run in 0.21 seconds

Thanks!
C.